1. Field of the Invention
This invention relates to an apparatus and a method of driving a plasma display panel, and more particularly to an apparatus and a method of driving a plasma display panel that are capable of being operated stable, regardless of temperature.
2. Description of the Related Art
A plasma display panel PDP is a display device using a phenomenon that visible ray is generated from a fluorescent substance when ultraviolet ray generated by gas discharge excites the fluorescent substance. The PDP is thinner and lighter than a cathode ray tube CRT, which has been used as main display means so far, and can be embodied of high definition and wide screen.
The PDP includes an upper substrate and a lower substrate installed facing each other with a barrier rib therebetween. The upper substrate includes the first and the second electrode formed in parallel to each other. A dielectric layer and a protective film are sequentially deposited on the first and the second electrode. The lower substrate includes an address electrode formed crossing with the first and the second electrode. A dielectric layer is formed on the address electrode to cover the address electrode. A discharge cell is positioned at an intersection of the address electrode and the first and the second electrode.
In order to express gray levels of a picture, such a PDP is driven by dividing one frame into various sub-fields having a different light-emission frequency. Each sub-field is divided again into a reset period for causing a uniform discharge, an address period for selecting a discharge cell and a sustaining period for implementing gray levels in dependence on discharge frequency.
In the reset period, a reset discharge is generated by a reset pulse supplied to the first electrode. And uniform wall charges are formed at the discharge cells by such a reset discharge. In the address period, a scanning pulse is supplied to the first electrode, and a data pulse synchronized with the scanning pulse is supplied to the address electrode. At this moment, an address discharge is generated at the discharge cells to which the scanning pulse and the data pulse are supplied. In the sustaining period, a sustaining pulse is alternately supplied to the first and the second electrode. If the sustaining pulse is supplied to the first and the second electrode, a sustaining discharge is generated at the discharge cell where the address discharge is generated.
When it is intended to display a picture of 256 gray levels, a frame period corresponding to 1/60second (i.e. 16.67 ms) is divided into 8 sub-fields SF1 to SF8. Herein, the reset period and the address period of each sub-field are equal every sub-field, whereas the sustaining period and the discharge frequency are increased at a ratio of 2n (Herein, n=0, 1, 2, 3, 4, 5, 6, 7 and 8) at each sub-field. As mentioned above, since the sustaining period is differentiated at each sub-field, gray levels of a picture can be displayed.
The conventional PDP driven in this way has a wrong discharge generated anywhere than at the area where its normal operation temperature is 0˜40° C. In other words, the wrong discharge phenomenon occurs below the temperature of 0° C. when experimenting performance characteristic of the PDP depending on the operation temperature. Particularly, when the PDP is operated below 0° C., a miswriting phenomenon occurs in the address period and a strong sustaining discharge, which is not intended, is generated in the sustaining period.
To describe more particularly, the scanning pulse supplied to the first electrode can be set at 1.3 μs, as in FIG. 1, in the address period of the PDP. If the scanning pulse set at a specific width in this way is supplied to the first electrode Y and the data pulse is supplied to the address electrode X, an address discharge is generated at the discharge cell. At this moment, because a discharge delay is small at the temperature not low (over 0° C.), a discharge occurrence time is positioned within a scanning pulse width, thereby generating a stable address discharge.
However, because the discharge delay is bigger at the low temperature (below 0° C.) than at the temperature not low, the discharge is possible not to be generated within the pulse width of the scanning pulse, i.e., 1.3 μs. In other words, the discharge occurrence time is positioned after the scanning pulse width by the discharge delay at the low temperature (below 0° C.), as shown in FIG. 1, to have the miswriting occur in the address period. On the other hand, the worse such a miswriting phenomenon occurs, the bigger the wide screen is and the higher the resolution is of the PDP.
Also, the polarization phenomenon of the dielectric layer formed on the upper and the lower substrate occurs faster at the temperature below 0° C. than at the temperature over 0° C.
Like this, if the polarization phenomenon of the dielectric layer occurs faster, the sustaining discharge can be easily generated with low voltage. Therefore, at the temperature below 0° C., the sustaining discharge generates a light with its brightness higher than an intended gray level.
On the other hand, because the discharge gas is activated, the discharge is easily generated with low voltage. Consequently, when the surrounding the temperature is over 40° C., the light is generated with its brightness higher than the intended gray level upon the sustaining discharge.